Nonvolatile memory, such as FLASH memory and EEPROM, has gained notoriety in the recent decade, namely due to its fast write time characteristics and ability to maintain storage of information even when no power is connected thereto. Nonvolatile memory is now employed in a wide number of applications, such as digital film for digital cameras, as a drive (or mass storage) in personal computers (PCs) or other hosts, hand-held electronic devices such as personal digital assistants (PDAs) and the like.
During manufacturing of nonvolatile memory devices, certain defects within the memory are detected and marked accordingly. Manufacturing defects are inherent in nonvolatile memory devices and other types of defects arise during use of the devices. Other types of defects can and generally result from repeated usage of the device. For example, a nonvolatile memory device is now generally expected to be used or re-written thereto anywhere from thousands to tens of thousands to hundreds of thousands to one million times and thereafter, the device typically becomes unusable due to the number of defective memory locations therein. As nonvolatile memory is utilized, it is written thereto for use in storing information and then it is erased prior to use of the same locations, i.e. re-written. In most applications, nonvolatile memory is organized into blocks and when a write is initiated by a host that is coupled to the memory, generally through a controller device, one or more blocks are written thereto. Prior to re-writing the one or more blocks, the latter need be erased and when a block undergoes anywhere from thousands to tens of thousands to hundreds of thousands to one million or so write and erase operations, it will generally become defective or its ability to store information reliably deteriorates. Thus, the more nonvolatile or flash memory is utilized, the more defects grow.
Additionally, nonvolatile memory has a limited capacity, which is basically, in large part, dependent upon the architecture or design of the nonvolatile memory. When nonvolatile memory devices are employed, data or information written thereto reduces the amount of available storage. The storage capacity of the nonvolatile memory clearly changes as its use changes. For example, initially, notwithstanding manufacturing defects, the storage capacity of the nonvolatile memory is 100% or the memory is completely available for storage. However, as information is stored therein, its storage capacity decreases until such time as when there is no further available locations for storage of information.
A computer system or host can always determine the amount of storage space remaining available for storage within a nonvolatile memory device. It should be noted that nonvolatile memory is intended to refer to any kind of memory, such as flash and EEPROM, that is capable of preserving information even when power is not being applied thereto. The storage capacity of a device, such as a card that includes nonvolatile memory is currently known by a host that is coupled to the nonvolatile memory generally through a controller device, but it is not displayed to the user of the card. Thus, in current nonvolatile systems, information regarding storage capacity is only available within the host and only when the nonvolatile memory device is coupled to the host.
Therefore, the need arises for a method and apparatus to measure and display the storage capacity of nonvolatile or flash memory of nonvolatile memory device(s) and to do so even when the nonvolatile memory device is not coupled to a host.